Proving and Improving the Flexibility of Vacuum Conveying

Most powder handling experts are aware of the hygienic advantages inherent in vacuum conveying equipment, but not everyone may be aware of the large amount of practical advantages that can be gained through building on this proven technology with innovative working practices. Designed primarily for the sanitary handling of powders, pellets and bulk granular product, vacuum handling systems are particularly ideal for long distance conveying.

Most powder handling experts are aware of the hygienic advantages inherent in vacuum conveying equipment, but not everyone may be aware of the large amount of practical advantages that can be gained through building on this proven technology with innovative working practices.

Designed primarily for the sanitary handling of powders, pellets and bulk granular product, vacuum handling systems are particularly ideal for long distance conveying.

Vacuum conveyors use air to convey powder materials safely, hygienically and economically over distances of up to 100m and at rates of up to 12000kg/hr.

Spiroflow recently rose to the challenge of building upon the significant advantages of vacuum conveying, and improving its practical benefits even further, when they were approached by a major international food manufacturer asking for help in the production of a flavored milk drink.

The client needed a system capable of transferring various flavored powders from Flexible Intermediate Bulk Containers (FIBCs) to an existing packing machine. This had to be performed at a variable throughput rate with a complete transfer of product despite the restricted headroom above the packing machine.

Furthermore, a quick and easy strip-down procedure was also required for the system in order to facilitate regular cleaning of the equipment in a local 'clean-down' room.

The solution supplied by Spiroflow incorporated a FIBC discharge unit fitted with pneumatic massage to promote product flow from the FIBC. To ensure that contaminates from the working environment did not get into the product, a hygiene tray was used and situated in a containment enclosure.

In this successful installation, when an FIBC is loaded into position for emptying, the bag liner is placed inside the hygiene tray while the outer fabric of the outlet is clamped around the outside in order to ensure complete containment.

Product discharged from the FIBC then passes through an integral Russell Finex sieve to remove any extraneous items or large friable lumps of product before it enters the vacuum transfer system.

This vacuum transfer system includes two in-feed hoppers, both of them being mobile and having their inlet and outlet assemblies fitted with tri-clover clips for easy disassembly when cleaning is required. Stainless transfer lines then take the product to the packing machine hopper.

A variable speed vacuum pump powers the whole system, giving the flexibility required on a production line to allow a range of different products to be conveyed.

The stainless steel vacuum filter receiver unit is mounted on a mobile frame fitted with lockable castors and a rotary blowing seal. A reverse jet filter cleaning system is utilized and a spare set of filters is supplied on a quick removal support plate to assist easy cleaning practices.

A high efficiency cyclone unit is mounted at the outlet of the conveying line above the packing machine which dis-entrains product from the conveying air. The cyclone was fitted with a pneumatically operated valve that facilitates the discharge of product to the packing machine hopper.

Due to height constraints above the client's packing machine, Spiroflow positioned the necessary filter-receiving unit above the product transfer line. This ensures that the small amount of product that was not dis-entrained in the high efficiency cyclone is recovered by the filters and returned to the product feed via the rotary blowing seal.

Conveyor throughput rates of 1500kg/hr are achieved by this system to contribute to maximizing production throughput.

Product transfer is initiated from a control panel located on the FIBC discharger and is controlled automatically using level sensors located in the packing machine. When a signal calling for product is received from the low-level control the vacuum pump and sieve are activated.

The vacuum unit alternates between two cycles. The first is the conveying cycle where the product is drawn into the cyclone chamber where it is dis-entrained from the air.

When a pre-determined volume of product is held, the vacuum relief valve operates and the system then changes to the 'dump' cycle where the product is released into the packing machine.

During the dump cycle the pump continues to run but the main barrel returns to atmospheric pressure. The reverse jet filter system then cleans the filters whilst the dump valve at the base of the cyclone opens to allow product into the filling machine hopper.

After a pre-set time the valve closes, whereupon the vacuum relief valve resets and the conveying cycle resumes, with the next batch of product being conveyed from the hopper.

When the high level switch in the filling machine is covered, the system completes the current transfer of product before stopping the conveyor. Once the low level switch is uncovered the cycle will be repeated.

The vacuum conveyor is cleaned between product runs. The system was designed to ensure the procedure was as quick and simple as possible for the operator.

First, the conveyor is operated with the air inlet valve fully closed. This has the effect of increasing the vacuum within the system to clear all remaining product from the line. A bag of sugar is then conveyed through the system to purge the vacuum lines of any residual dust.

Utilizing the quick-release features of the equipment, the operator then disconnects the short length of flexible vacuum pipe that connects the feeder to the stainless steel tubing and the hopper is removed from the sieve.

This allows the inlet hopper to be wheeled away and to be replaced by a clean one that can be reconnected up to the main line. This breakdown procedure can be completed within a few minutes by just one operator.

The upper reverse jet filter portion of the vacuum filter unit is unclamped using the quick-release couplings, allowing the operator access to the main barrel of the unit where the filters are stored on a support plate.

In addition to the normal quick-release clamps, the filters were also designed for fast removal without the need for tools. This enables them to be easily taken away for dry cleaning.

The whole filter unit can then be disconnected from the main lines via its tri-clover clamps, to be wheeled away to the cleaning area on its own self-contained mobile frame where an operator will be able to dry clean the inside of the unit. The main barrel can be removed on the quick-release clips to allow direct access to the blowing seal for cleaning.

Once completed, a clean set of filters can be placed in the main barrel and the top section re-clamped in position. The complete clean-down requires only about 60 to 90 minutes.

Because of the modular construction of these units, they can be easily adapted to meet a wide variety of different user needs and are particularly attractive to companies in the food and pharmaceutical sectors.

Furthermore, the designs and materials of construction can be varied to adapt the systems for any company involved in the processing and handling of powders or granules.
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